Twadio: Legal music sharing via Twitter

Okay, this is not exactly P2P, but it's pretty ingenious nonetheless: Twadio is a Twitter bot that tweets the title of a new song every 15 minutes.

Most of the songs are pretty popular, so there's a good chance you'll instantly remember the tune and listen to it - in your head. From the site:

"Twadio is a radio station you can't hear. Through the magic of Twitter, it plants a new song in your brain every few minutes. Just follow the Tweejay and it'll play you the tunes right inside your head."